This invention is related to the field of robotics, and, more particularly, to a method for controlling a legged robot so that the robot is capable of walking and running over terrain containing hills and over surfaces affording limited traction. The invention is also related to the realistic animation of legged creatures walking and running over rough terrain.
Much prior art concerning legged mechanical devices, including robots, exists. These approaches have been capable of statically stable walking only.
However, the prior art for the dynamic locomotion of robots is sparse. In the late 1970s, a laboratory apparatus for studying hopping with active control of balance was made and was the first successful device which operated with dynamic legged locomotion. Subsequently the first successful running machines were described. These machines are designed to work on flat surfaces affording good traction and are incapable of negotiating an irregular or slippery surface during legged running. In passing, the term, "running," is used herein in the conventional sense, i.e., a motion such that all the legs of the creature/animal/robot are off the ground at the same time.
Some development of dynamic control of legged machines over rough terrain has occurred. There has been some work on slip control of legged machines on difficult surfaces. However, all of this work is basically conservative in approach, suitable only for slow, careful walking.
Even in the computerized animation of legged creatures, automated slip control for a more realistic representation of running has not been developed. For example, Badler, N., Barsky, A., and Zeltzer, D., "Making them Move: Mechanics, Control, and Animation of Articulated Figures", 1991, Morgan Kaufmann, ISBN 1-55860-106-6, a book-length overview of animation of legged creatures, fails to mention any slip control for the animated figures. In the movie, Jurassic Park, the animated dinosaurs were not animated using physically-based modelling techniques. Rather, the motion of the dinosaurs was manually adjusted to the terrain with computers "drawing" the creatures after the adjustment. The most advanced physically-based animation of legged running appears to be for flat ground, with occasional hops over small obstacles. The problems introduced by slippery surfaces or hills is not addressed.
The present invention solves or substantially mitigates these problems. With the present invention, legged robots are capable of running over hills and slippery surfaces. Furthermore, the present invention provides for the realistic operation of a robotic leg which is jointed similarly to animal legs. Finally, the animation of legged creatures is made more efficiently and more realistic. Leg slip and movements over inclined slopes are automatically determined in accordance with the present invention for realistic simulations. Realistic effects are enhanced with the simulated operation of legs jointed similarly to animal legs.